Conventionally, a plurality of solar panels used in a solar power system are installed by being arranged in an orderly manner without providing level-differences or clearances in vertical and horizontal directions.
For example, there proposed a solar panel mounting method in Japanese Patent Laid-Open No. 2010-209515 in which rectangular solar panels are arranged on top of a frame provided on the roof of a building without providing level-differences or clearances (Patent Literature 1). It is necessary to make the size compact by removing level-differences or clearances since the area on the roof is limited, and in consideration of appearance, a solar panel group arranged in an orderly manner without providing level-differences or clearances features a beautiful appearance to see since the panel group is installed at a conspicuous location on the roof.